Gymnocalycium tillianum

Gymnocalycium tillianum is a short, squat Argentinian cactus, with shining green stems that grow 10 cm tall and 15 cm wide. It has long, black-brown, curving spines and relatively large pale pink, carmine red or wine-red flowers in spring that stand out. The richness of the red always provides an inner glow of satisfaction. Spherical fruit follow in summer. Gymnocalycium tillianum is almost identical to the standard Gymnocalycium oenanthemum and it is hard to tell apart one from the others, if not for the geographical provenance and a few little differences in seeds morphology and they are not considered distinct.

Stem: Solitary, flattened globose, leaf-green, grey-green or bluish-green; up to 12-15 cm in diameter, and 8-10 cm tall. Apex depressed, woolly, covered by the spines from neighboring areoles.
Roots: Fibrous.
Ribs: 11 to 13 (12 to 18 according to Ritter), sinuous, acute or somewhat rounded, separated by deep vertical furrows. Tubercles rounded, with prominent chins separates by straight transverse furrows, occupying the whole width of the ribs.
Areoles: Oblong, 8 × 5 mm, initially yellow then white.
Radial spines: 5 (3 to 8, Ritter), stout, stiff, erect, , straight to slightly curved, 25-30 mm long one pointing downward, others in pairs curving sideways. .
Central spines: absent (occasionally one is present, similar to the radial, Ritter), erect and slightly bent upwards. Young spines translucent, grey-brown with dark tip to blackish, becoming grey with brownish points.
Flowers: Apical, 30-35 mm long, 25-35(-40) mm in diameter. Pericarpel short (15 mm), green, with rounded olive-green scales, initially edged with white and a pink point, then bordered with pink. Outer perianth segments spatulate, cherry-red with an olive-green wide median band. Inner perianth segments spatulate, but narrower, with a small mucro, carmine red. Throat carmine. Filaments carmine pink. Anthers light yellow. Style carmine to orange-red. Stigma white to yellowish, with 9-11 lobes, under the stamens.
Fruits: Flattened globose to spherical, light green to brownish green with lighter scales.
Seeds: ca. 1 mm. Testa matt blackish-brown, finely granulous. Hilum large basal, circled with a strong prominent white ring.

Watering: Needs moderate to copious waterings in summer, but do not overwater (Rot prone), keep dry in winter at a minimum temperature of 0°C.
Fertilization: Feed with a high potassium fertilizer in summer.
Hardiness: Reputedly resistant to frost if kept on the dry side prior to, and during, cold weather (hardy to -5 C ° C, or less for short periods).
Exposition: The plant tolerates extremely bright situations but enjoys filtered sunlight or afternoon shade, inside it needs bright light, and some direct sun. Tends to bronze in strong light, which encourages flowering and heavy spine production, but is likely to suffer from sun scorch or stunted growth if over exposed to direct sunlight during the hottest part of the day in summer. In full sun turns an uneven brownish red colour.

Some of the information in this description has been found at desert-tropicals.com, llifle.com and cactus-art.biz